Semiconductor device

ABSTRACT

A semiconductor device is capable of stably maintaining a voltage level of a shield line, even when a voltage level of an adjacent line is varied. The semiconductor device includes normal lines arranged for transfer of signals, a shield line arranged adjacently to the normal lines, a level shifting circuit for receiving an input signal swinging between a power supply voltage level and a ground voltage level, and shifting the input signal to an output signal swing between the power supply voltage level and a low voltage level lower than the ground voltage level by a predetermined level to output a shifted signal via the shield line, and a signal input unit for transferring the signal provided via the shield line to an output node.

CROSS-REFERENCE TO RELATED APPLICATION

The present invention claims priority of Korean patent applicationnumber 10-2006-0068123, filed on Jul. 20, 2006, which is incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device; and, moreparticularly, to a semiconductor device having a shield line.

As well-known in the art, a semiconductor device is a semiconductordevice for storing quantities of data. This semiconductor device can belargely divided into a data storage area storing data and a peripheralarea for effectively accessing the data stored in the data storage area.The data storage area has a plurality of unit cells for storing acorresponding number of data bits. The peripheral area has a data outputcircuit for receiving the data stored in the data storage area andoutputting the data externally, a data input circuit for conveyingexternally received data to the data storage area, and an address inputcircuit for receiving addresses for designating locations of data to beaccessed. In addition, the peripheral area further has a mode registerwhich stores information that enables the above circuits to operatenormally. For example, the mode register stores information such as aburst length denoting the number of data bits output during a singledata access, a Column Address Strobe (CAS) latency denoting a time froman input of the address to an output of corresponding data, and so on.

In the general semiconductor device, the data input circuit, the dataoutput circuit and the address input circuit are circuits that arecontinuously operated during a data access operation. On the other hand,circuits such as the mode register are not operated for every dataaccess, but are operated only when the semiconductor device sets relatedinformation during an initial operation. Therefore, once each of linesor wires associated with the mode register is designated at one level,is the level need not be varied while a data access operation isperformed.

The semiconductor device employs these lines as shield lines of otherlines in order to effectively arrange internal circuits and lines.However, one shortcoming is that there may be an error due to avariation of a voltage level of each line which is under the protectionof the shields lines. Namely, the shield lines are influenced by leveltransition of the lines which are under the protection of the shieldslines, thus making it possible to transition to an opposite levelwithout maintaining an originally required level.

FIG. 1 is a diagram showing coupling capacitors between lines.

Referring to FIG. 1, there are provided a shield line S, lines A1 and A2that are under the protection of the shield line, and couplingcapacitors Cc1 and Cc2 disposed therebetween. In addition, there is aparasitic capacitor Csb between the shield line S and a substrate. Whena voltage level of the lines A1 and A2 rises from a ground voltage levelto a power supply voltage level, a voltage of the shield line S arrangedtherebetween will rise by ΔVc. At this time, the risen level affects theoperation of circuits coupled to the shield line, and thus, a level ofsignal other than a predetermined level may be output via the shieldline S. An equation shown in FIG. 1 is derived under the assumption thatno charge additionally flows into the lines A1 and A2. Actually, sincethe semiconductor device has a driver for driving the lines A1 and A2,the variation widths of the lines A1 and A2 may be different from eachother depending on the driving capability of the driver driving thelines A1 and A2 and resistance thereof.

FIG. 2 is a diagram for more particularly describing the problem causedby the coupling capacitors shown in FIG. 1.

With reference to FIG. 2, a shield line S is arranged for transferring asignal output from a signal output unit 10 to a signal input unit 20.The signal transferred through the shield line S is not intended to bevaried once it is set, such as the signal required when the memorydevice is initially sets. Therefore, in a normal mode that allows thememory device to perform a data access operation, a level of a signalapplied to the shield line S is not varied if it is set once.

It is first assumed that the shield line S is maintained at a logic lowlevel and a signal is continuously delivered to each of the lines A1 andA2 adjacent to the shield line S. When the signal to each of the linesA1 and A2 rises from the ground voltage level to the power supplyvoltage, the voltage level of the shield line S rises by ΔVb by thecoupling effect. At this time, if the voltage level by the risen voltageΔVb is higher than a threshold voltage of MOS transistors arranged inthe signal input unit 20, the MOS transistor MN2 is turned on. When theMOS transistor MN2 is turned on, a voltage level at a node N2transitions from a logic high level to a logic low level. This impliesthat a normally set signal is changed to an improper level which maycause an error in the operation of the semiconductor device.

The above problem may also be caused when the voltage level of theshield line S is maintained at a logic high level. In this case, whenthe voltage level of the lines A1 and A2 drops from a logic high levelto a logic low level, the voltage level of the shield line S can dropfrom the logic high level by ΔVb. Because of the dropped voltage by ΔVb,when the MOS transistor MP2 is turned on, the level at the node N2 cantransition from the logic low level to the logic high level. This alsoimplies that a normally set signal is changed to an improper level,which makes the semiconductor device malfunction and cause any errortherein. In order to solve the above problem, the shield line caninclude a dummy line through which no signal is transferred, but in thiscase, a circuit size is increased.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide asemiconductor device which is capable of stably maintaining a voltagelevel of a shield line, even when a voltage level of an adjacent line isvaried.

In accordance with one aspect of the present invention, there isprovided a semiconductor device, including: normal lines arranged fortransfer of signals; a shield line arranged adjacently to the normallines; a level shifting circuit for receiving an input signal swingingbetween a power supply voltage level and a ground voltage level, andshifting the input signal to an output signal swing between the powersupply voltage level and a low voltage level lower than the groundvoltage level by a predetermined level to output a shifted signal viathe shield line; and a signal input unit for transferring the signalprovided via the shield line to an output node.

In accordance with another aspect of the present invention, there isprovided a semiconductor device, including: normal lines arranged fortransfer of signals; a shield line arranged adjacently to the normallines; a level shifting circuit for receiving an input signal swingingbetween a power supply voltage level and a ground voltage level, andshifting the input signal to an output signal swing between a highvoltage level higher than the power supply voltage level and the groundvoltage level to output a shifted signal via the shield line; and asignal input unit for transferring the signal provided via the shieldline to an output node.

In accordance with still another aspect of the present invention, thereis provided a semiconductor device, including: normal lines arranged fortransfer of signals; a shield line arranged adjacently to the normallines; a level shifting circuit for receiving an input signal swingingbetween a power supply voltage level and a ground voltage level, andshifting the input signal to an output signal swinging between a highvoltage level higher than the power supply voltage level by apredetermined level and a low voltage level lower than the groundvoltage level by a predetermined level to output a shifted signal viathe shield line; and a signal input unit for transferring the signalprovided via the shield line to an output node.

In accordance with still yet another aspect of the present invention,there is provided a method for driving a semiconductor device, includingthe steps of: generating a control signal to maintain a ground voltagelevel; driving a voltage level on a shield line to a low voltage lowerthan the ground voltage by a predetermined level by using the controlsignal; and transferring the signal under the state that the shield lineis being driven.

In accordance with a further another aspect of the present invention,there is provided a method for driving a semiconductor device, includingthe steps of: generating a control signal to maintain a power supplyvoltage level; driving a voltage level on a shield line to a highvoltage higher than the power supply voltage by a predetermined level byusing the control signal; and transferring the signal under the statethat the shield line is being driven.

In accordance with an additional aspect of the present invention, thereis provided a method for driving a semiconductor device, including thesteps of: generating an input signal swinging between a power supplyvoltage level and a ground voltage level; level-shifting the inputsignal to a driving signal swinging between a high voltage level higherthan the power supply voltage by a predetermined level and a low voltagelevel lower than the ground voltage level by a predetermined level;driving a shield line by using the driving signal; and transferring thesignal under the state that the shield line is being driven.

Other objectives and advantages of the invention will be understood bythe following description and will also be appreciated by theembodiments of the invention more clearly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing coupling capacitors between lines.

FIG. 2 is a diagram for describing the problem caused by the couplingcapacitors shown in FIG. 1.

FIG. 3 is a circuit diagram of a semiconductor device in accordance witha first embodiment of the present invention.

FIG. 4 is a detailed circuit diagram of the low level shifter shown inFIG. 3.

FIG. 5 is a waveform diagram representing the operation of thesemiconductor device shown in FIG. 3.

FIG. 6 is a circuit diagram of a semiconductor device in accordance witha second embodiment of the present invention.

FIG. 7 is a detailed circuit diagram of the high level shifter shown inFIG. 5.

FIG. 8 is a waveform diagram representing the operation of thesemiconductor device shown in FIG. 6.

FIG. 9 is a circuit diagram of a semiconductor device in accordance witha third embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be setforth in detail with reference to the accompanying drawings to theextent so that a person skilled in the art can easily carry out theinvention.

FIG. 3 is a circuit diagram of a semiconductor device in accordance witha first embodiment of the present invention.

Referring to FIG. 3, the semiconductor device of this embodimentincludes normal lines A1 and A2 arranged for transfer of signal, ashield line Sb arranged adjacently to the normal lines A1 and A2, alevel shifting circuit 110 for receiving an input signal N1 swingingbetween a power supply voltage VDD level and a ground voltage VSS level,shifting the input signal to an output signal swinging between the powersupply voltage VDD level and a low voltage level VBB lower than theground voltage VSS level by a predetermined level and outputting theoutput signal via the shield line Sb, and a signal input unit 120 fortransferring the signal provided via the shield line Sb to an outputnode. The normal lines A1 and A2 are arranged in regions adjacent to oneside and the other side of the shield line Sb respectively.

The level shifting circuit 110 is provided with a low level shifter 111for level-shifting a level of the input signal to swing between thepower supply voltage VDD and the low voltage level VBB, and a driver 112for driving the shield line Sb by using the signal level-shifted by thelow level shifter 111.

The driver 112 is provided with a PMOS transistor MP3 whose one side isconnected to the power supply voltage supplying terminal VDD and gatereceives an output of the level shifter 111, and an NMOS transistor MN3whose one side is connected to the other side of the PMOS transistorMP3, gate receives the output of the level shifter 111, and other sideis connected to the low voltage supplying terminal VBB.

The signal input unit 120 is provided with a pull-down MOS transistorMN4 for pulling-down the output node N2 by using the signal transferredvia the shield line Sb. The low voltage VBB is lower than the groundvoltage VSS by a threshold voltage level of the MOS transistor MN4.

A line in which a certain voltage level is set during an initialoperation of the semiconductor device and the set voltage level is notvaried during a normal operation is mainly used as the shield line Sb.In the case of the semiconductor device, when an active operation and aprecharge operation, a write/read operation and a refresh operation arecarried out, a line through which a signal is maintained at a constantlevel without any variation of its phase may be applied as the shieldline. For example, in the case of the semiconductor device, the signaldelivered through the shield line Sb can be at least one of a signal forcontrolling a burst length of the semiconductor device, a signal forcontrolling a CAS latency, a control signal for controlling on/offoperations of a delay locked loop, a control signal for controlling OnDie Terminal (ODT), a control signal for deciding a driving capabilityof the output driver 112, a control signal for controlling timing ofwrite recovery, a control signal for controlling a test mode and thelike.

The level shifter 111 may be located at the front end of the driver 112or at any other place. For instance, if a signal to be applied to theshield line is generated by decoding diverse signals, the level shiftermay be arranged at the front end of a decoder (not shown) forlevel-shifting the signal before decoding it. In such a case, thedecoder decodes an output signal of the level shifter and then conveys adecoded signal to the shield line.

Further, in the semiconductor device, a voltage maintaining a levellower than the ground voltage and used as a bulk voltage may be employedas the low voltage VBB as it is. In this case, it does not need to havea separate generator for generating the low voltage VBB.

FIG. 4 is a detailed circuit diagram of the low level shifter shown inFIG. 3.

Referring to FIG. 4, the low level shifter 111 is provided with a PMOStransistor M1 whose one side is connected to the power supply voltagesupplying terminal VDD and gate receives the input signal IN, aninverter 13 receiving the input signal IN via an input terminal, a PMOStransistor M2 whose one side is connected to the power supply voltagesupplying terminal VDD and gate receives an output of the inverter I3,an NMOS transistor M3 whose one side is connected to the other side ofthe PMOS transistor M1, gate is connected to the other side of the PMOStransistor M2, and other side is connected to the low voltage supplyingterminal VBB through which the low voltage is supplied, and an NMOStransistor M4 whose one side is connected to the other side of the PMOStransistor M2, gate is connected to the other side of the PMOStransistor M1, and other side is connected to the low voltage supplyingterminal VBB.

FIG. 5 is a waveform diagram representing the operation of thesemiconductor device shown in FIG. 3. The operation of the semiconductordevice of this embodiment will be described in detail with reference toFIGS. 3 to 5.

Referring to the left side of the waveform shown in FIG. 5, if a voltagelevel on the shield line is maintained at the ground voltage level, avoltage at the node N2 is varied in an undesired direction by avariation of a signal passing through its adjacent lines A1 and A2,which may cause an error.

As shown in the right side of the waveform in FIG. 5, the semiconductordevice of this embodiment maintains the low voltage level VBB, ratherthan maintaining the ground voltage level VSS, if the shield line ismaintained at the logic low level. Here, the low voltage is maintainedat a level lower than the ground voltage level VSS by a thresholdvoltage of the MOS transistor MN4 constituting the signal input unit120.

Although the voltage level applied to the shield line Sb has risen byΔVb due to a transition of a signal passing through the adjacent linesA1 and A2, the MOS transistor MN4 of the signal input unit 120 is notturned on at an undesired time since it has risen from the low voltageVBB level by ΔVb. Therefore, although the voltage level on the shieldline Sb is varied by the coupling effect, the signal transferred throughthe node N2 is maintained in the original state. Namely, the node N2 isallowed to be maintained at the power supply voltage level.

FIG. 6 is a circuit diagram of a semiconductor device in accordance witha second embodiment of the present invention.

Referring to FIG. 6, the semiconductor device of this embodimentincludes normal lines A1 and A2 arranged for transfer of signal, ashield line Sb arranged adjacent to the normal lines A1 and A2, a levelshifting circuit 210 for receiving an input signal N1 swinging between apower supply voltage VDD level and a ground voltage VSS level, andshifting the input signal to an output signal swinging between a highvoltage VPP higher than the power supply voltage VDD level and theground voltage VSS level to output a shifted signal via the shield lineSb, and a signal input unit 220 for transferring the signal provided viathe shield line Sb to an output node N2.

The level shifting circuit 210 is provided with a high level shifter 211for level-shifting a level of the input signal IN to swing between thehigh voltage VPP and the ground voltage VSS level, and a driver 210 fordriving the shield line Sb by using a signal Sa level-shifted by thehigh level shifter 211.

The driver 212 is provided with a PMOS transistor MP4 whose one side isconnected to the power supply voltage supplying terminal VDD and gatereceives an output of the level shifter 211, and an NMOS transistor MN5whose one side is connected to the other side of the PMOS transistorMP4, gate receives the output of the level shifter 211, and other sideis connected to the ground voltage supplying terminal VSS.

The signal input unit 220 is provided with a pull-up MOS transistor MP5for pulling-up the output node N2 by using the signal transferred viathe shield line Sb. The high voltage VPP is characterized by beinghigher than the ground voltage VSS by a threshold voltage level of theMOS transistor MP5.

A line in which a certain voltage level is set during an initialoperation of the semiconductor device and the set voltage level is notvaried during a normal operation is mainly used as the shield line Sb.In the case of the semiconductor device, when an active operation and aprecharge operation, a write/read operation and a refresh operation arecarried out, a line through which a signal is maintained at a constantlevel without any variation of its phase may be applied as the shieldline. For example, in the case of the semiconductor device, the signaldelivered through the shield line Sb can be at least one of a signal forcontrolling a burst length of the semiconductor device, a signal forcontrolling a CAS latency, a control signal for controlling on/offoperations of a delay locked loop, a control signal for controlling ODT,a control signal for deciding a driving capability of the output driver,a control signal for controlling timing of write recovery, a controlsignal for controlling a test mode and the like.

The level shifter 211 may be located at the front end of the driver 212or at any other place. For instance, if a signal to be applied to theshield line is generated by decoding diverse signals, the level shiftermay be arranged at the front end of a decoder (not shown) forlevel-shifting the signal before decoding it. In such a case, thedecoder decodes an output signal of the level shifter and then conveys adecoded signal to the shield line.

Further, in the semiconductor device, a word line activation voltagemaintaining a level higher than the power supply voltage may be used asthe high voltage VPP as it is. In this case, it does not need to have aseparate generator for generating the high voltage VPP.

FIG. 7 is a detailed circuit diagram of the high level shifter shown inFIG. 5.

Referring to FIG. 7, the high level shifter 211 includes an NMOStransistor M7 with one side connected to a ground voltage supplyingterminal VSS and a gate receiving an input signal IN, an inverter I4receiving the input signal IN via an input terminal, an NMOS transistorM8 with one side connected to the ground voltage supplying terminal VSSand a gate receiving an output of the inverter I4, a PMOS transistor M5with one side connected to the other side of the NMOS transistor M7, agate connected to the other side of the NMOS transistor M8, and otherside connected to a high voltage supplying terminal VPP through whichthe high voltage VPP is supplied, and a PMOS transistor M6 with one sideconnected to the other side of the NMOS transistor M8, a gate connectedto the other side of the NMOS transistor M8, and other side connected tothe high voltage supplying terminal VPP.

FIG. 8 is a waveform diagram representing the operation of thesemiconductor device shown in FIG. 6. Hereinafter, the operation of thesemiconductor device of this embodiment will be described in detail withreference to FIGS. 6 to 8.

Referring to the left side of the waveform shown in FIG. 8, if theshield line is maintained to the power supply voltage VDD, a voltage atthe node N2 is varied in an undesired direction by a variation of asignal passing through its adjacent lines A1 and A2, which may cause anyerror.

But, as in the right side of the waveform shown in FIG. 8, thesemiconductor device of this embodiment maintains the high voltage VPPlevel, rather than maintaining the power supply voltage VDD level, ifthe voltage level on the shield line is maintained at the high level.Here, the high voltage VPP is maintained to be a level higher than thepower supply voltage VDD level by a threshold voltage of the MOStransistor MP5 constituting the signal input unit 220.

Although the voltage level applied to the shield line Sb has dropped byΔVb by a transition of a signal passing through the adjacent lines A1and A2, the MOS transistor MP5 of the signal input unit 220 is notturned on at an undesired time since it has dropped from the highvoltage VPP level by ΔVb. Therefore, although the voltage level on theshield line Sb is varied by the coupling effect, the signal transferredthrough the node N2 is resultantly maintained in the original state.Namely, the node N2 is allowed to be maintained at the ground voltageVSS level.

FIG. 9 is a circuit diagram of a semiconductor device in accordance witha third embodiment of the present invention.

Referring to FIG. 9, the semiconductor device of this embodimentincludes normal lines A1 and A2 arranged for transfer of signal, ashield line Sb arranged adjacent to the normal lines A1 and A2, a levelshifting circuit 310 for receiving an input signal N1 swinging between apower supply voltage VDD level and a ground voltage VSS level, andshifting the input signal to an output signal swinging between a highvoltage VPP level higher than the power supply voltage VDD level by apredetermined level and a low voltage VBB level lower than the groundvoltage VSS level by a predetermined level to output a shifted signalvia the shield line Sb, and a signal input unit 320 for transferring thesignal provided via the shield line Sb to an output node N2.

The semiconductor device of the third embodiment is implemented bycombining the semiconductor devices of the first and the secondembodiments. Therefore, since an operation of the semiconductor deviceof the third embodiment is similar to the operations of thesemiconductor devices of the first and the second embodiments, adetailed description thereon will be omitted here for simplicity.

One difference is that driving voltages of a low level shifter 312 arethe high voltage VPP and the low voltage VBB since it receives an outputsignal of a high level shifter 311. The high level shifter 311 and thelow level shifter 312 can be configured by using the circuits as shownin FIGS. 7 and 4, respectively. In addition, the signal input unit 320is provided with both a pull-up MOS transistor MP7 and a pull-down MOStransistor MN7.

As set forth above, the present invention has an advantage in that afinal node connected to a shield line can be allowed to be maintained ata desired signal although the shield line is affected by a transition ofa signal in the process of transfer of a signal on lines adjacent to theshield line. Accordingly, according to the present invention, the lineswhich carry a signal maintaining a constant value during a normaloperation such as an initial setting operation as in the prior art canbe continuously used as the shield line.

Furthermore, in a circuit receiving the signal on the shield line, agate bias of an NMOS transistor at an input end is lower than a sourcebias, and a gate bias of a PMOS transistor at an input end is higherthan a source bias. Thus, leakage current can be reduced by the MOStransistors coupled with the input end.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. A semiconductor device, comprising: normal lines arranged fortransfer of signals; a shield line arranged adjacent to the normallines; a level shifting circuit for receiving an input signal swingingbetween a power supply voltage and a ground voltage, and shifting theinput signal to level-shifted signal swinging between the power supplyvoltage and a low voltage lower than the ground voltage by apredetermined level so that a logic state of an output signal output toan output node is maintained regardless of variations of the signals ofthe normal lines; and a signal input unit in response to thelevel-shifted signal provided via the shield line to selectively couplethe output node to the ground voltage, wherein the signal input unitincludes a pull-down circuit for receiving the level-shifted signal andthe predetermined level is equal to or greater than a threshold voltageof the pull-down circuit.
 2. The semiconductor device as recited inclaim 1, wherein the level shifting circuit includes: a low levelshifter for level-shifting a level of the input signal to swing betweenthe power supply voltage and the low voltage; and a driver for drivingthe shield line by using the signal level-shifted by the low levelshifter.
 3. The semiconductor device as recited in claim 2, wherein thelow level shifter includes: a first PMOS transistor having one sideconnected to the power supply voltage supplying terminal and a gatecoupled to the input signal; an inverter receiving the input signal viaan input terminal; a second PMOS transistor having one side connected toa power supply voltage supplying terminal and a gate coupled to anoutput of the inverter; a first NMOS transistor having one sideconnected to a second side of the first PMOS transistor, a gateconnected to a second side of the second PMOS transistor, and a secondside connected to a low voltage supplying terminal through which the lowvoltage is supplied; and a second NMOS transistor having one sideconnected to the second side of the second PMOS transistor, a gateconnected to the second side of the first PMOS transistor, and a secondside connected to the low voltage supplying terminal.
 4. Thesemiconductor device as recited in claim 3, wherein the driver includes:a third PMOS transistor having one side connected to the power supplyvoltage supplying terminal and a gate coupled to an output of the levelshifter; and a third NMOS transistor having one side connected to thesecond side of the third PMOS transistor, a gate coupled to an output ofthe level shifter, and a second side connected to the low voltagesupplying terminal.
 5. The semiconductor device as recited in claim 1,wherein the pull-down circuit comprises a MOS transistor having one sideconnected to the output node, a gate connected to the shield line, and asecond side connected to the ground voltage supplying terminal.
 6. Thesemiconductor device as recited in claim 5, wherein the low voltage islower than the ground voltage by a level above a threshold voltage ofthe MOS transistor.
 7. The semiconductor device as recited in claim 1,wherein the normal lines are disposed in a region adjacent to one sideof the shield line and a region adjacent to the other side of the shieldline, respectively.
 8. The semiconductor device as recited in claim 1,wherein the shield line is a line in which a predetermined voltage levelis set during an initial operation of the semiconductor device and thevoltage level is not varied during a normal operation.
 9. Thesemiconductor device as recited in claim 1, wherein the input signaltransferred through the shield line is at least one of a signal forcontrolling a burst length of a semiconductor device, a signal forcontrolling a Column Address Strobe (CAS) latency, a control signal forcontrolling on/off operations of a delay locked loop, a control signalfor controlling On Die Terminal (ODT), a control signal for deciding adriving capability of the output driver, a control signal forcontrolling a timing of write recovery, and a control signal forcontrolling a test mode.
 10. A method for driving a semiconductor deviceincluding normal lines for transfer of signals and a shield lineadjacent to the normal lines, comprising the steps of: receiving aninput signal swinging between a power supply voltage and a groundvoltage; shifting the input signal to a level-shifted signal swingingbetween the power supply voltage and a low voltage lower than the groundvoltage by a predetermined level so that a logic state of an outputsignal output to an output node is maintained regardless of variationsof signals of the normal lines; and in response to the level-shiftedsignal provided via the shield line, selectively coupling the outputnode to the ground voltage by using a pull-down circuit to receive thelevel-shifted signal, wherein the predetermined level is equal to orgreater than a threshold voltage of the pull-down circuit.
 11. Themethod as recited in claim 10, wherein the shifting step includes thesteps of: shifting a signal level of the input signal to the lowvoltage; and driving the shield line by using the level-shifted signal.12. The method as recited in claim 11, wherein the low voltage is lowerthan the ground voltage by a level above a threshold voltage of a MOStransistor.
 13. The method as recited in claim 10, wherein the shieldline is a line in which a predetermined voltage level is set during aninitial operation of the semiconductor device and the voltage level isnot varied during a normal operation.
 14. The method as recited in claim10, wherein the input signal transferred through the shield line is atleast one of a signal for controlling a burst length of a semiconductordevice, a signal for controlling a CAS latency, a control signal forcontrolling on/off operations of a delay locked loop, a control signalfor controlling ODT, a control signal for deciding a driving capabilityof an output driver, a control signal for controlling a timing of writerecovery, and a control signal for controlling a test mode.